I wasn't trying to make a plea for community consensus. I think individuals come to their own conclusions about morality, but those conclusions are informed by the information that they receive from their environment and community. A person who never experiences meaningful debate, thought, or contemplation is going to be morally stunted compared to those who engage in regular debate and discussion. That doesn't mean every person who argues a point is morally superior, but in the aggregate, engaging in moral discussions will enhance an individuals expertise in determining moral veracity.

I think you are improperly comparing community consensus with tragedy of the commons. Community consensus is more akin to regulation than it is to nash equilibria. It's the nash equilibria that has been a bad heuristic for finding the global happiness maxima, because it's through the nash equilibria that the tragedy of the commons occurs. In contrast, effective regulation can better ensure the global happiness maxima. So that's why community dialogue and a rough consensus of mores can be useful and productive towards the health of a society.